Root/kernel/trace/trace_stat.c

1/*
2 * Infrastructure for statistic tracing (histogram output).
3 *
4 * Copyright (C) 2008-2009 Frederic Weisbecker <fweisbec@gmail.com>
5 *
6 * Based on the code from trace_branch.c which is
7 * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
8 *
9 */
10
11
12#include <linux/list.h>
13#include <linux/slab.h>
14#include <linux/rbtree.h>
15#include <linux/debugfs.h>
16#include "trace_stat.h"
17#include "trace.h"
18
19
20/*
21 * List of stat red-black nodes from a tracer
22 * We use a such tree to sort quickly the stat
23 * entries from the tracer.
24 */
25struct stat_node {
26    struct rb_node node;
27    void *stat;
28};
29
30/* A stat session is the stats output in one file */
31struct stat_session {
32    struct list_head session_list;
33    struct tracer_stat *ts;
34    struct rb_root stat_root;
35    struct mutex stat_mutex;
36    struct dentry *file;
37};
38
39/* All of the sessions currently in use. Each stat file embed one session */
40static LIST_HEAD(all_stat_sessions);
41static DEFINE_MUTEX(all_stat_sessions_mutex);
42
43/* The root directory for all stat files */
44static struct dentry *stat_dir;
45
46/*
47 * Iterate through the rbtree using a post order traversal path
48 * to release the next node.
49 * It won't necessary release one at each iteration
50 * but it will at least advance closer to the next one
51 * to be released.
52 */
53static struct rb_node *release_next(struct tracer_stat *ts,
54                    struct rb_node *node)
55{
56    struct stat_node *snode;
57    struct rb_node *parent = rb_parent(node);
58
59    if (node->rb_left)
60        return node->rb_left;
61    else if (node->rb_right)
62        return node->rb_right;
63    else {
64        if (!parent)
65            ;
66        else if (parent->rb_left == node)
67            parent->rb_left = NULL;
68        else
69            parent->rb_right = NULL;
70
71        snode = container_of(node, struct stat_node, node);
72        if (ts->stat_release)
73            ts->stat_release(snode->stat);
74        kfree(snode);
75
76        return parent;
77    }
78}
79
80static void __reset_stat_session(struct stat_session *session)
81{
82    struct rb_node *node = session->stat_root.rb_node;
83
84    while (node)
85        node = release_next(session->ts, node);
86
87    session->stat_root = RB_ROOT;
88}
89
90static void reset_stat_session(struct stat_session *session)
91{
92    mutex_lock(&session->stat_mutex);
93    __reset_stat_session(session);
94    mutex_unlock(&session->stat_mutex);
95}
96
97static void destroy_session(struct stat_session *session)
98{
99    debugfs_remove(session->file);
100    __reset_stat_session(session);
101    mutex_destroy(&session->stat_mutex);
102    kfree(session);
103}
104
105typedef int (*cmp_stat_t)(void *, void *);
106
107static int insert_stat(struct rb_root *root, void *stat, cmp_stat_t cmp)
108{
109    struct rb_node **new = &(root->rb_node), *parent = NULL;
110    struct stat_node *data;
111
112    data = kzalloc(sizeof(*data), GFP_KERNEL);
113    if (!data)
114        return -ENOMEM;
115    data->stat = stat;
116
117    /*
118     * Figure out where to put new node
119     * This is a descendent sorting
120     */
121    while (*new) {
122        struct stat_node *this;
123        int result;
124
125        this = container_of(*new, struct stat_node, node);
126        result = cmp(data->stat, this->stat);
127
128        parent = *new;
129        if (result >= 0)
130            new = &((*new)->rb_left);
131        else
132            new = &((*new)->rb_right);
133    }
134
135    rb_link_node(&data->node, parent, new);
136    rb_insert_color(&data->node, root);
137    return 0;
138}
139
140/*
141 * For tracers that don't provide a stat_cmp callback.
142 * This one will force an insertion as right-most node
143 * in the rbtree.
144 */
145static int dummy_cmp(void *p1, void *p2)
146{
147    return -1;
148}
149
150/*
151 * Initialize the stat rbtree at each trace_stat file opening.
152 * All of these copies and sorting are required on all opening
153 * since the stats could have changed between two file sessions.
154 */
155static int stat_seq_init(struct stat_session *session)
156{
157    struct tracer_stat *ts = session->ts;
158    struct rb_root *root = &session->stat_root;
159    void *stat;
160    int ret = 0;
161    int i;
162
163    mutex_lock(&session->stat_mutex);
164    __reset_stat_session(session);
165
166    if (!ts->stat_cmp)
167        ts->stat_cmp = dummy_cmp;
168
169    stat = ts->stat_start(ts);
170    if (!stat)
171        goto exit;
172
173    ret = insert_stat(root, stat, ts->stat_cmp);
174    if (ret)
175        goto exit;
176
177    /*
178     * Iterate over the tracer stat entries and store them in an rbtree.
179     */
180    for (i = 1; ; i++) {
181        stat = ts->stat_next(stat, i);
182
183        /* End of insertion */
184        if (!stat)
185            break;
186
187        ret = insert_stat(root, stat, ts->stat_cmp);
188        if (ret)
189            goto exit_free_rbtree;
190    }
191
192exit:
193    mutex_unlock(&session->stat_mutex);
194    return ret;
195
196exit_free_rbtree:
197    __reset_stat_session(session);
198    mutex_unlock(&session->stat_mutex);
199    return ret;
200}
201
202
203static void *stat_seq_start(struct seq_file *s, loff_t *pos)
204{
205    struct stat_session *session = s->private;
206    struct rb_node *node;
207    int n = *pos;
208    int i;
209
210    /* Prevent from tracer switch or rbtree modification */
211    mutex_lock(&session->stat_mutex);
212
213    /* If we are in the beginning of the file, print the headers */
214    if (session->ts->stat_headers) {
215        if (n == 0)
216            return SEQ_START_TOKEN;
217        n--;
218    }
219
220    node = rb_first(&session->stat_root);
221    for (i = 0; node && i < n; i++)
222        node = rb_next(node);
223
224    return node;
225}
226
227static void *stat_seq_next(struct seq_file *s, void *p, loff_t *pos)
228{
229    struct stat_session *session = s->private;
230    struct rb_node *node = p;
231
232    (*pos)++;
233
234    if (p == SEQ_START_TOKEN)
235        return rb_first(&session->stat_root);
236
237    return rb_next(node);
238}
239
240static void stat_seq_stop(struct seq_file *s, void *p)
241{
242    struct stat_session *session = s->private;
243    mutex_unlock(&session->stat_mutex);
244}
245
246static int stat_seq_show(struct seq_file *s, void *v)
247{
248    struct stat_session *session = s->private;
249    struct stat_node *l = container_of(v, struct stat_node, node);
250
251    if (v == SEQ_START_TOKEN)
252        return session->ts->stat_headers(s);
253
254    return session->ts->stat_show(s, l->stat);
255}
256
257static const struct seq_operations trace_stat_seq_ops = {
258    .start = stat_seq_start,
259    .next = stat_seq_next,
260    .stop = stat_seq_stop,
261    .show = stat_seq_show
262};
263
264/* The session stat is refilled and resorted at each stat file opening */
265static int tracing_stat_open(struct inode *inode, struct file *file)
266{
267    int ret;
268    struct seq_file *m;
269    struct stat_session *session = inode->i_private;
270
271    ret = stat_seq_init(session);
272    if (ret)
273        return ret;
274
275    ret = seq_open(file, &trace_stat_seq_ops);
276    if (ret) {
277        reset_stat_session(session);
278        return ret;
279    }
280
281    m = file->private_data;
282    m->private = session;
283    return ret;
284}
285
286/*
287 * Avoid consuming memory with our now useless rbtree.
288 */
289static int tracing_stat_release(struct inode *i, struct file *f)
290{
291    struct stat_session *session = i->i_private;
292
293    reset_stat_session(session);
294
295    return seq_release(i, f);
296}
297
298static const struct file_operations tracing_stat_fops = {
299    .open = tracing_stat_open,
300    .read = seq_read,
301    .llseek = seq_lseek,
302    .release = tracing_stat_release
303};
304
305static int tracing_stat_init(void)
306{
307    struct dentry *d_tracing;
308
309    d_tracing = tracing_init_dentry();
310
311    stat_dir = debugfs_create_dir("trace_stat", d_tracing);
312    if (!stat_dir)
313        pr_warning("Could not create debugfs "
314               "'trace_stat' entry\n");
315    return 0;
316}
317
318static int init_stat_file(struct stat_session *session)
319{
320    if (!stat_dir && tracing_stat_init())
321        return -ENODEV;
322
323    session->file = debugfs_create_file(session->ts->name, 0644,
324                        stat_dir,
325                        session, &tracing_stat_fops);
326    if (!session->file)
327        return -ENOMEM;
328    return 0;
329}
330
331int register_stat_tracer(struct tracer_stat *trace)
332{
333    struct stat_session *session, *node;
334    int ret;
335
336    if (!trace)
337        return -EINVAL;
338
339    if (!trace->stat_start || !trace->stat_next || !trace->stat_show)
340        return -EINVAL;
341
342    /* Already registered? */
343    mutex_lock(&all_stat_sessions_mutex);
344    list_for_each_entry(node, &all_stat_sessions, session_list) {
345        if (node->ts == trace) {
346            mutex_unlock(&all_stat_sessions_mutex);
347            return -EINVAL;
348        }
349    }
350    mutex_unlock(&all_stat_sessions_mutex);
351
352    /* Init the session */
353    session = kzalloc(sizeof(*session), GFP_KERNEL);
354    if (!session)
355        return -ENOMEM;
356
357    session->ts = trace;
358    INIT_LIST_HEAD(&session->session_list);
359    mutex_init(&session->stat_mutex);
360
361    ret = init_stat_file(session);
362    if (ret) {
363        destroy_session(session);
364        return ret;
365    }
366
367    /* Register */
368    mutex_lock(&all_stat_sessions_mutex);
369    list_add_tail(&session->session_list, &all_stat_sessions);
370    mutex_unlock(&all_stat_sessions_mutex);
371
372    return 0;
373}
374
375void unregister_stat_tracer(struct tracer_stat *trace)
376{
377    struct stat_session *node, *tmp;
378
379    mutex_lock(&all_stat_sessions_mutex);
380    list_for_each_entry_safe(node, tmp, &all_stat_sessions, session_list) {
381        if (node->ts == trace) {
382            list_del(&node->session_list);
383            destroy_session(node);
384            break;
385        }
386    }
387    mutex_unlock(&all_stat_sessions_mutex);
388}
389

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